There are still plenty of older senators around — the median age of the current Senate is 61, and there are 23 in their 70s or 80s — but these days when we think of a presidential candidate emerging from Congress’ upper chamber, we no longer imagine someone who has spent decades amassing a legislative record, like so many party nominees before, in the mold of John Kerry or Bob Dole. Instead, the senators who today decide to make a run for the presidency are the ones who just got there and can’t seem to wait to get out.

That may mean we’ve stopped thinking that a deep understanding of legislation is much of a requirement for the presidency. Once again, Barack Obama may have proven this point. Despite his modest résumé as a lawmaker, his first two years in the White House saw the passage of an extraordinary number of significant bills, none more so than health care reform, a decades-old Democratic priority that Bill Clinton (with his famous people skills) failed to achieve. Though the model of the legislator-as-president was Lyndon Johnson, people forget that the Great Society was made possible by the fact that Johnson enjoyed huge Democratic majorities after 1964, with over two-thirds of the seats in both houses held by his party. Passing all those programs still wasn’t easy, but it would have been impossible in a more closely divided Congress, let alone one controlled by Republicans, no matter how good a persuader and vote-counter Johnson was.